function Map(linkItems) {
	this.current = undefined;
	this._size = 0;
	if (linkItems === false) {
		this.disableLinking();
	}
}
/**
 * 获取当前map
 * 
 * @return 当前对象
 */
Map.noop = function() {
	return this;
};
/**
 * 非法操作
 * 
 * @return
 */
Map.illegal = function() {
	throw new Error("非法操作，Map已经被禁用");
};
/**
 * 
 * @param obj
 * @param foreignKeys
 * @return
 */
Map.from = function(obj, foreignKeys) {
	var map = new Map;
	for ( var prop in obj) {
		if (foreignKeys || obj.hasOwnProperty(prop)) {
			map.put(prop, obj[prop]);
		}
	}
	return map;
};
/**
 * 禁用map
 * 
 * @return
 */
Map.prototype.disableLinking = function() {
	this.link = Map.noop;
	this.unlink = Map.noop;
	this.disableLinking = Map.noop;
	this.next = Map.illegal;
	this.key = Map.illegal;
	this.value = Map.illegal;
	this.clear = Map.illegal;
	return this;
};
/**
 * 返回hash值 例如：number 123
 * 
 * @param value
 *            key/value
 * @return
 */
Map.prototype.hash = function(value) {
	return (typeof value)
			+ ' '
			+ (value instanceof Object ? (value.__hash || (value.__hash = ++arguments.callee.current)) : value
					.toString());
};
/**
 * 返回map的长度
 * 
 * @return
 */
Map.prototype.size = function() {
	return this._size;
};

Map.prototype.hash.current = 0;
/**
 * 通过key获取value
 * 
 * @param key
 * @return
 */
Map.prototype.get = function(key) {
	var item = this[this.hash(key)];
	return item === undefined ? undefined : item.value;
};
/**
 * 向map中添加数据
 * 
 * @param key
 *            键
 * @param value
 *            值
 * @return
 */
Map.prototype.put = function(key, value) {
	var hash = this.hash(key);
	if (this[hash] === undefined) {
		var item = {
			key : key,
			value : value
		};
		this[hash] = item;
		this.link(item);
		++this._size;
	} else {
		this[hash].value = value;
	}
	return this;
};
/**
 * 通过key删除数据
 * 
 * @param key
 * @return
 */
Map.prototype.remove = function(key) {
	var hash = this.hash(key);
	var item = this[hash];
	if (item !== undefined) {
		--this._size;
		this.unlink(item);
		delete this[hash];
	}
	return this;
};
/**
 * 清除map
 * 
 * @return
 */
Map.prototype.clear = function() {
	while (this._size) {
		this.remove(this.key());
	}
	return this;
};
/**
 * 处理队列
 * 
 * @param item
 * @return
 */
Map.prototype.link = function(item) {
	if (this._size == 0) {
		item.prev = item;
		item.next = item;
		this.current = item;
	} else {
		item.prev = this.current.prev;
		item.prev.next = item;
		item.next = this.current;
		this.current.prev = item;
	}
};
Map.prototype.unlink = function(item) {
	if (this._size == 0) {
		this.current = undefined;
	} else {
		item.prev.next = item.next;
		item.next.prev = item.prev;
		if (item === this.current) {
			this.current = item.next;
		}
	}
};
/**
 * 获取下一个
 * 
 * @return
 */
Map.prototype.next = function() {
	this.current = this.current.next;
	return this;
};
/**
 * 获取key
 * 
 * @return
 */
Map.prototype.key = function() {
	return this.current.key;
};
/**
 * 获取value
 * 
 * @return
 */
Map.prototype.value = function() {
	return this.current.value;
};